Hansen's involvement was disclosed by California's campaign watchdog Friday. He issued a statement saying he "made a mistake" by giving a Los Angeles law firm $100,000. The firm secretly funneled $80,000 to a group gathering signatures to force a public vote on the arena plan.

The Fair Political Practices Commission sued to learn Hansen's identity. Hansen tried to buy the Sacramento Kings and move them to Seattle until his bid was denied by the NBA earlier this year. The team's new owners are working with city officials to build the team a downtown arena to replace the aging facility the Kings now call home. But a Los Angeles law firm secretly donated $80,000 to a group gathering signatures to force a public vote on the arena plan.

The California Fair Political Practices Commission filed a lawsuit Thursday to learn the donor's identity and revealed during a Friday news conference that it was Hansen.

Gary Winuk, chief of the commission's enforcement division, said Hansen donated $100,000 just a month after the NBA denied his attempt to move the team. It was not immediately clear what happened to the additional $20,000 that was not reported by opponents who want to force a public vote before the arena can be built on the site of what is now a shopping mall blocks from the state Capitol.

The $20,000 is believed to still be with a political consultant who acted as middleman to funnel the money from Hansen to the Los Angeles law firm, Loeb & Loeb, and then to the group opposing the arena, Winuk said. He said the investigation is continuing.